Breathing assistance apparatus

ABSTRACT

A mouthpiece for oral delivery for oral delivery of CPAP treatment has a vestibular shield for location between the teeth and lips/cheeks of a wearer. The vestibular shield is dimensioned to extend laterally into the buccal vestibule and vertically to overlap the gums. The vestibular shield is formed from a very supple material. A gases pathway is provided through the vestibular shield and may include a hard plastic insert through the shield, including a standard breathing conduit connection at its outer end. A short stub conduit on the outlet side of the shield passes between the wearers upper and lower teeth.  
     A connection for connecting the mouthpiece to a breathing circuit is also provided which reduces the transfer of forces caused by movement therebetween. The connection may include a short length of highly flexible gases conduit, an elbow and a swivel connection.

BACKGROUND OF THE INVENTION

[0001] 1. Field of Invention

[0002] This invention relates to a system for oral delivery of gasespressurized above ambient, and in particular, to a system, including anovel mouthpiece, for the oral delivery of air in continuous positiveairway pressure (CPAP) treatments of sleeping disorders such as sleepapnoea.

[0003] 2. Description of the Prior Art

[0004] Sleep apnoea treatments have been significantly advanced with theintroduction of continuous positive airway pressure (CPAP) treatments.These treatments, as introduced, involve the supply of gases from agases supply or blower to a patient through a conduit and nasal mask toprovide an elevated internal pressure in the users airways to assist themuscles to keep the airways open. This airstream is provided to the userthrough a nasal mask applied over the nose and held in place by aharness. This configuration has been almost universally adopted based onthe well known observation that humans show a decided preference fornasal breathing during sleep. For this reason, little development hasbeen undertaken into other possible methods of providing the pressurizedairstream to a user.

[0005] Oral delivery is suggested in EP 818, 213, which shows anapparatus for oral delivery of air in a CPAP treatment. The apparatusincludes a mouthpiece adapted to fit inside the mouth between the roofof the mouth, the hard palate, and the tongue, and having a peripherywhich can be gripped between the teeth. It is thought by the applicantsthat this is significantly more intrusive than is necessary and isliable to movement and consequent discomfort (although not outrightremoval) under the relaxation of sleep. It has the additionaldisadvantage that with the user fully relaxed, such as in the case ofsleep, a distension in the user's jaw and subsequent opening of themouth can reduce the sealing effectiveness of the mouthpiece and reducethe efficacy of the CPAP treatment.

[0006] Because the mouthpiece in EP 818,213 is gripped between theuser's teeth, a further disadvantage results in that the mouthpiecerequires custom orthodontic fitting to ensure that the mouthpiecematches the user's mouth and teeth layout. Custom orthodontic fitting istime consuming and removes the capability of effective mass manufacture.Consequently, the mouthpiece in EP 818,213 is expensive, creating asignificant barrier to the patient adoption of the device.

[0007] A similar gases delivery mouthpiece, for use with a respirator,is shown in WO 90/03199. WO 90/03199 discloses an orthodontic devicewhich is adapted to be gripped between the jaws of a user and toaccommodate the user's teeth within a series of upper and lowercavities. A base member of the mouthpiece is shaped and fits against thehard palate of the user. This mouthpiece again has the disadvantage ofrequiring custom orthodontic fitting. Furthermore, as a result of themouthpiece's substantial thickness and size, the mouthpiece issubstantially rigid in the vestibule regions of the mouth. Themouthpiece is clamped in place by an outer shield which engages theoutside of the user's lips.

[0008] A paper by E Veres entitled “Clinical trial of an oral vestibularshield for the control of snoring” (Journal of the Dental Association ofSouth Africa, January 1993) describes the use of a shield intended to beretained in the vestibule of the mouth to seal the mouth and to promotenasal breathing which has been conventionally considered to be morebeneficial than oral breathing. Humidified CPAP treatments deliveredorally, however, actually derive greater benefit than those deliverednasally because secondary leakage through the nasal passages during oraldelivery is significantly less than oral leakage during nasal delivery.The shield depicted in the paper is formed from flexible ethylene vinyl.The shield is custom trimmed and is custom fitted by heating to amalleable temperature and deformed by applied pressure.

[0009] Other possible mouthpiece designs are shown for example by use inself contained underwater breathing apparatus systems, for example asdepicted in U.S. Pat. No. 4,862,909. This mouthpiece is a mouth guardtype and is clamped between the teeth. A flange extends both in front ofand behind the teeth.

[0010] Prior art mouthpieces are not well adapted for use in CPAPtreatments because they are intended for conscious gripping by the user,and have been found subject to accidental removal with a user in acompletely relaxed state such as sleep. The present invention overcomesthis problem and present several other advantages which will becomeapparent upon a reading of the attached specification, in combinationwith a study of the drawings.

SUMMARY OF THE INVENTION

[0011] It is an object of the present invention to provide a system fororal delivery of gases, and/or a mouthpiece for oral delivery of gases,which goes some way toward overcoming the above disadvantages or whichwill at least provide the public with a useful choice.

[0012] Accordingly in a first aspect the present invention consists in asystem capable of being used for oral delivery of gases pressurizedabove ambient to a user comprising: a mouthpiece; a breathing tube; anddecoupling means for connecting said mouthpiece to said breathing tube,said decoupling means comprising a connection tube being formed of amaterial which is more flexible than the material of which saidbreathing tube is formed.

[0013] In a second aspect the present invention consists in a mouthpiececomprising: a generally rectangularly-shaped vestibular shield having aninner surface and an outer surface, said vestibular shield having apredetermined height which will overlap a user's teeth and gums whenpositioned in the mouth vestibule of a user, said vestibular shieldhaving a central portion which will extend over a user's front teeth andgums when said central portion of said vestibular shield is positionedbetween the lips and the teeth of the user, and outer portions extendingfrom said central portion which extend along and overlap at least aportion of the user's back teeth and gums when said outer portions ofsaid vestibular shield are positioned between the cheeks and the teethof the user; and gases passageway means extending from said outersurface of said vestibular shield to said inner surface of saidvestibular shield for allowing the passage of said gases through saidmouthpiece.

[0014] In a third aspect the present invention consists in a mouthpiececomprising:

[0015] a vestibular shield having an inner surface and an outer surface,said vestibular shield having a predetermined height which will overlapa user's teeth and gums when positioned in the mouth vestibule of auser;

[0016] gases passageway means extending from said outer surface of saidvestibular shield to said inner surface of said vestibular shield forallowing the passage of said gases through said mouthpiece; and

[0017] extra-oral sealing means associated with said gases passagewaywhich may be adjusted into one of two configurations, a first conditionwhen said mouthpiece is inserted into a user's mouth being substantiallyunengaged with a user's face, and a second condition when correctlypositioned in a user's mouth being substantially engaged with a user'sface and under compression thereupon.

[0018] In a fourth aspect in a first aspect the present inventionconsists in a system capable of being used for oral delivery of gasespressurized above ambient to a user comprising:

[0019] gases supply means,

[0020] a gases passageway in fluid communication with said gases supplymeans, and

[0021] a mouthpiece in fluid communication with said gases passagewayincluding an intra-oral sealing means and an extra-oral sealing means.

[0022] To those skilled in the art to which the invention relates, manychanges in construction and widely differing embodiments andapplications of the invention will suggest themselves without departingfrom the scope of the invention as defined in the appended claims. Thedisclosures and the descriptions herein are purely illustrative and arenot intended to be in any sense limiting.

[0023] The invention consists in the foregoing and also envisagesconstructions of which the following gives examples.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] One preferred form of the present invention will now be describedwith reference to the accompanying drawings in which;

[0025]FIG. 1 is a side elevational view of the system according to thepresent invention as being used by a patient,

[0026]FIG. 2 is a perspective view from above of a mouthpiece accordingto the preferred embodiment of the present invention,

[0027]FIG. 3 is a perspective view from one side and from an inwarddirection of the mouthpiece of FIG. 2,

[0028]FIG. 4 is a cross-section of the mouthpiece of FIG. 2,

[0029]FIG. 5 is a cross-sectional view of the mouthpiece of FIG. 2 and auser with the mouthpiece in place to demonstrate the location andpositioning thereof in relation to the main features of the user'sanatomy,

[0030]FIG. 6 is a perspective view of the mouthpiece with the outer flapin place,

[0031]FIG. 7 is a perspective view of the outer flap bent back,

[0032]FIG. 8 is a cutaway view of the present invention with the outerflap in use,

[0033]FIG. 9 is a perspective view of the outer flap including theventilation apertures and moisture barrier, and

[0034]FIG. 10 is a block diagram of a respiratory system according tothe preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] While the invention may be susceptible to embodiment in differentforms, there is shown in the drawings, and herein will be described indetail, specific embodiments with the understanding that the presentdisclosure is to be considered an exemplification of the principles ofthe invention, and is not intended to limit the invention to that asillustrated and described herein.

[0036] The present invention provides a novel system for oral deliveryof gases pressurised above ambient to a user and is especially suitedfor use in the oral delivery of air in continuous positive airwaypressure (CPAP) treatments of sleeping disorders such as sleep apnoea.As shown in FIG. 1, the system includes a mouthpiece 1 which isconnected by a connection 40 to a breathing circuit 41.

[0037] A preferred embodiment of the present invention is illustrated inFIGS. 2 to 5. In this embodiment, the mouthpiece 50 includes avestibular shield 2 being a generally flat and generallyrectangularly-shaped member in front elevation having a curved profilethat reflects the curvature of a user's jaw and in turn the curvature ofthe labial vestibule region. A gases passageway extends through thevestibular shield from an inlet 51 to an outlet 52 in much the same wayas with the earlier embodiments. In the preferred embodiment the inlet51 is provided by a flattened oval-shaped connector 53. The outlet 52has an even more laterally extended flattened oval shape 54. The majordifferences between the mouthpiece 50 and the embodiments describedabove are provided on the inner face of the vestibular shield. Mostprominently, the mouthpiece 50 includes a tongue depressor 55 extendingfrom the inner face of the vestibular shield 2. The operation of thetongue depressor will be described further on with reference to FIG. 5.The tongue depressor includes a vertical stiffening flange 56 centrallylocated on its upper surface and extending from the gases outlet 52. Inuse gases flow easily around the stiffening flange 56 effectivelybifurcating the gases outlet 52. The tongue depressor 55 furtherincludes a pair of vertically extending spacers 57 which in use may abutagainst the roof of the wearer's mouth and ensure that the tongue cannotcompletely block the air passageway. In the mouthpiece 50 the sealingeffect of the vestibular shield 2 against the lips of the user isenhanced by providing teeth abutments of significantly increasedthickness than the raised area 20 of the earlier embodiments. Inparticular, an upper teeth abutment 58 and a lower teeth abutment 59 areprovided, with the lower teeth abutment 59 protruding further from theinner face of the vestibular shield 2 than the upper teeth abutment 58.This difference serves to match the typical over-bite of most users. Theabutments 58 and 59 are not required to be wider than the gases outlet52.

[0038] A notch 60 is provided centrally in the upper edge of thevestibular shield 2 to accommodate the upper frenal attachment. A slightbead 61 is provided around the edge of the vestibular shield 2 for usercomfort, with the vestibular shield 2 otherwise being very thin foradditional suppleness.

[0039] Referring particularly to FIG. 4, in its preferred form themouthpiece 50 is preferably formed by over-moulding a soft and supplematerial part 70 over a stiffer material part 67. These can generally betermed the shield part and the passageway-forming insert. Thepassageway-forming insert preferably includes a pair of upper and lowervertical flanges 63 and 64 to fully engage within the supple material.The passageway-forming insert 67 includes the vertically extendingstiffening flange 56 of the tongue depressor 55, together with a curvedplanar portion 71 forming the backbone of the tongue depressor 55. Thevertically extending spacers 57 are of the soft and supple material andare part of the over-moulding 70, as are the upper and lower teethabutments 58 and 59.

[0040] Referring now to FIG. 5, use of the mouthpiece according to FIGS.2 to 4 is depicted. With the present mouthpiece 50, the upper and lowerlips 5, 6 are further distended by the abutment action of the abutments75, 76 against the upper and lower teeth 7, 8 respectively, thus forminga seal of greater pressure between the lips 5, 6 and the upper and lowerportions respectively of the vestibular shield 2. A lower face 77 of thetongue depressor 55 impinges if necessary on the upper surface 72 of thetongue 25 and retains the tongue in the lower portion of the mouth. Thisensures a clear gases outlet 52 from the gases passageway through thevestibular shield. The vertically extending spacers 57, if forced bypressure from the tongue, will engage against the roof of the user'smouth and maintain a clear air passageway. This stops the sleepingpatient unconsciously blocking the oral passageway and reverting tonasal breathing.

[0041] Attention is now directed to FIG. 1. It has been found that anadditional factor in the effectiveness of any mouthpiece, includingmouthpiece 1, is the manner in which the mouthpiece is connected to thebreathing circuit 41. The weight of the breathing circuit 41, and anyattempted movement of one other of the breathing circuit 41 and themouthpiece 1 relative to the other, is one of the largest influencestending to dislodge a mouthpiece 1 from the mouth of a user. It must benoted that the mouthpiece 1 must remain in position and maintain a sealduring all sleep, when the user has no muscle tone.

[0042] The connection 40 as provided in the present invention betweenthe breathing circuit 41 and the mouthpiece 1 decouples the mouthpiece 1from the breathing circuit 41. As a result, the connection 40 iseffective in reducing the forces placed on the mouthpiece 1 by thebreathing circuit 41 when the user moves around during sleep. In thepreferred sleeping position, the breathing circuit 41 is laid across thechest 43 of the user, and may be secured to the user's bed clothes orsleeping garments. The breathing circuit 41 is preferably laid on thechest of the user to take the weight of the breathing circuit 41 off ofthe mouthpiece 1.

[0043] To connect between the gases outlet 14 which is vertical when theuser is laying on his or her back and the breathing circuit 41 which isgenerally horizontal, an L-shaped elbow 45 is incorporated in theconnection 40. The elbow 45 may be incorporated in the mouthpiece 1,however, it is preferred that the mouthpiece 1 be kept small to providefor easier cleaning. The elbow 45 is formed at a right angle andprovides a positive pressure on the mouthpiece 1 to maintain themouthpiece 1 in the user's mouth. The elbow 45 may include a swiveljoint and may be disconnected from gaseous outlet 14. The connection 40further includes an extremely flexible connecting tube 46 providedbetween the elbow 45 and the breathing circuit 41. The connecting tube46 is preferably connected to the breathing circuit 41 by a swivel joint48 for reasons described herein. The breathing circuit 41, whileflexible, will necessarily be stiff enough to maintain its integrityover comparatively long tuns, while the connecting tube 46, being only ashort length, for example 10 centimetres, merely has to span between theuser's mouth and chest, and can thereby be made in a manner that wouldnot be suitable for long runs. Furthermore, as a result of the shortlength of the connecting tube 46, the connecting tube 46 does not needto incorporate significant insulation or heating capability. Theconnecting tube 46 may be formed from a thin plastic membrane supportedover a helical or double helical or corrugated supporting ribs. In sucha case, the support makes the connection tube 46 laterally flexible andresistant to torsion. The elbow swivel joint 45 allows for movement ofthe connection tube 46 relative to the mouthpiece 1. The swivel joint 48allows for movement of the connection tube 46 relative to the breathingcircuit 41. It is to be understood that one or both of the swivel joints45, 48 could be eliminated, but the preferred embodiment includes swiveljoint 48.

[0044] Referring now to FIG. 6 of the present invention is illustratedincluding an extra-oral sealing flap 100. The flap 100 in its naturalbias is tapered, the wide open end of which is shaped to conform to thefacial contours around the outside of the mouth of a user. The narrowend joins to a cylindrical section, which is designed to slide over theinlet port 104 of the mouthpiece 102. While this is one method ofattachment the flap 100 might also be constructed as an integral part ofthe mouthpiece 102. The flap 100 needs to be constructed of flexiblematerial, therefore materials such as silicone rubber can be employed tofashion the flap.

[0045] The outer flap 100 is seen in FIG. 7, in a bent back position. Itwill be appreciated that when the mouthpiece 102 is being inserted intothe mouth of a user, the outer flap 100 is intended to be in this bentback position to aid insertion. Prior to insertion, the outer flap isbent back by simply pressing on its outer periphery 106, until it snapsinto the bent back position, in which it will stay unaided.

[0046] In FIG. 8 we see the outer flap 100 in use with the mouthpiece102 in the mouth 107 of a user 110. Once correctly positioned in themouth 106, the outer flap 100 may be adjusted into its operationalposition by pressing on its outer periphery 106 until it snaps back topress against the outside of the mouth 108. Due to the relative positionof the vestibular shield 112 and the outer flap 100, the outer flap 100is unable to fully reach its natural bias and thereby inflicts acompressive force on the outside of the mouth 108.

[0047] It will be appreciated that as well as providing a substantiallyairtight seal the addition of the outer flap provides enough compressiveforce on the mouth to keep the mouthpiece and conduit in place withoutthe need for straps. This allows the administering of CPAP therapy to beconsiderably less obtrusive than traditional methods.

[0048] In a further additional improvement shown in FIG. 9, the outerflap 300 is shown in perspective. Included are ventilation apertures302, 303 either side of the gases port 304, which are surrounded by aridge 306 acting as a moisture barrier. The apertures 302,303 areprovided such that any excess moisture leaking from the mouth willmigrate to the apertures where they may evaporate. Small vents in theconduit may be used to direct small amounts of pressurised gas at theapertures to aid evaporation. The ridge 306 is included to ensure thatno moisture migrates further into the sealing region 308, as this wouldbe detrimental to the sealing properties of the flap.

[0049] A typical respiratory humidification circuit such as might employthe present invention is shown diagrammatically in FIG. 10, and includesthe respirator 230, humidifier 231, and the associated respiratorybreathing tubes 233 and 234. A patient 236 under treatment is shown,with the present invention 237, located in the mouth of the patient 236.

[0050] From the above it can be seen that the present invention providesa system including mouthpiece 1 for oral delivery of CPAP treatmentwhich at once is low cost and effective. Unlike other appliances themouthpiece 1 used in the present invention does not require customorthodontic fitting as the mouthpiece 1 does not rely on accuratealignment with the user's teeth or the user's palate to provide locationand retention within the user's mouth, but instead resides in thevestibule between the teeth and lips and the teeth and cheeks, and thelateral and vertical extension of the vestibular shield 2 requires thatthe user's lips be actively manipulated for the vestibular shield 2 tobe removed. Furthermore the improved connection 40 to the breathingcircuit 41 reduces the forces which tend to pull at the mouthpiece 1.With the addition of the extra-oral flap 100, the mouthpiece andassociated tubing is held securely in place without the need forexternal strapping, and an effective seal is created around the usersmouth.

1. A system capable of being used for oral delivery of gases pressurizedabove ambient to a user comprising: a mouthpiece; a breathing tube; anddecoupling means for connecting said mouthpiece to said breathing tube,said decoupling means comprising a connection tube being formed of amaterial which is more flexible than the material of which saidbreathing tube is formed.
 2. A system as claimed in claim 1 wherein saidconnection tube is shorter in length than said breathing tube.
 3. Asystem as claimed in claim 1 wherein said connection tube is formed froma thin plastic membrane supported over one or more helical supportingribs.
 4. A system as claimed in claim 1 wherein said connection tube isformed from a thin plastic membrane supported over one or morecorrugated supporting ribs.
 5. A system as claimed in claim 1 whereinsaid decoupling means further includes a swivel joint between saidconnection tube and said breathing tube.
 6. A system as claimed in claim1 wherein said decoupling means further includes an L-shaped elbowconnected between said mouthpiece and said connection tube.
 7. A systemas claimed in claim 6 wherein said L-shaped elbow includes a swiveljoint.
 8. A system as claimed in claim 1 wherein said mouthpieceincluding sealing means with an intra-oral portion and an extra-oralportion.
 9. A system as claimed in claim 8 wherein said extra-oralportion may be adjusted into one of two configurations, a firstconfiguration when said mouthpiece is inserted into said user's mouthbeing substantially unengaged with said user's face, and a secondconfiguration when correctly positioned in said user's mouth beingsubstantially engaged with said user's face and under compressionthereupon.
 10. A mouthpiece comprising: a generally rectangularly-shapedvestibular shield having an inner surface and an outer surface, saidvestibular shield having a predetermined height which will overlap auser's teeth and gums when positioned in the mouth vestibule of a user,said vestibular shield having a central portion which will extend over auser's front teeth and gums when said central portion of said vestibularshield is positioned between the lips and the teeth of the user, andouter portions extending from said central portion which extend alongand overlap at least a portion of the user's back teeth and gums whensaid outer portions of said vestibular shield are positioned between thecheeks and the teeth of the user; and gases passageway means extendingfrom said outer surface of said vestibular shield to said inner surfaceof said vestibular shield for allowing the passage of said gases throughsaid mouthpiece.
 11. A mouthpiece as claimed in claim 10 wherein saidmouthpiece further includes a raised portion provided on said innersurface of said central portion of said vestibular shield, said raisedportion solely contacting the teeth of a user when said vestibularshield is placed in the mouth of a user.
 12. A mouthpiece as claimed inclaim 11 wherein said raised portion is of a generally flattened ovalshape.
 13. A mouthpiece as claimed in claim 12 wherein said raisedportion extends along at least a portion of said outer portions.
 14. Amouthpiece as claimed in claim 10 wherein said central portion includesa centrally located notch in a top edge thereof.
 15. A mouthpiece asclaimed in claim 10 wherein said vestibular shield has a generallycurved profile.
 16. A mouthpiece as claimed in claim 10 wherein saidgases passageway means includes gases inlet means for allowingconnecting of said mouthpiece to a gases supply.
 17. A mouthpiece asclaimed in claim 10 wherein said gases inlet means is connected to saidcentral portion of said vestibular shield.
 18. A mouthpiece as claimedin claim 10 wherein said vestibular shield is formed of a supplematerial and said gases inlet means comprises a tube formed of a stiffermaterial than said supple material that is used to form said vestibularshield, said tube being attached to said vestibular shield.
 19. Amouthpiece as claimed in claim 10 wherein said gases passageway meansincludes gases outlet means for allowing gases to be expelled into themouth of a user.
 20. A mouthpiece as claimed in claim 19 wherein saidgases outlet means is provided along said central portion of saidvestibular shield.
 21. A mouthpiece as claimed in claim 20 wherein saidgases passageway means includes gases inlet means for allowingconnection of said mouthpiece to a gases supply.
 22. A mouthpiece asclaimed in claim 21 wherein said gases outlet means is aligned with saidgases inlet means.
 23. A mouthpiece as claimed in claim 22 wherein saidgases inlet means and said gases outlet means are connected to saidcentral portion of said vestibular shield.
 24. A mouthpiece as claimedin claim 23 wherein said gases outlet means is a generally flattenedoval-shaped tube which extends from said inner surface of saidvestibular shield.
 25. A mouthpiece as claimed in claim 24 wherein saidouter portions of said vestibular shield include a plurality of ribsthereon.
 26. A mouthpiece as claimed in claim 25 wherein said ribs areprovided on said outer surface of said vestibular shield.
 27. Amouthpiece as claimed in claim 26 wherein said vestibular shield isformed of a supple material.
 28. A mouthpiece as claimed in claim 27wherein said vestibular shield is generally flat.
 29. A mouthpiece asclaimed in claim 28 wherein each said outer portion has rounded upperand lower edges.
 30. A mouthpiece as claimed in claim 11 wherein saidraised portion includes an upper abutment portion for abutting againstthe upper teeth and a lower abutment portion for abutting against thelower teeth and the lower abutment portion is raised further from theinner surface of the vestibular shield than said upper abutment portion.31. A mouthpiece as claimed in claim 10 including a tongue depressingguard extending from the inner side of said vestibular shield.
 32. Amouthpiece as claimed in claim 31 wherein said tongue depressor has aconcave curve in its lower surface and is stiffer than the outerportions of said vestibular shield.
 33. A mouthpiece as claimed in claim32 wherein said mouthpiece including one or more vertically extendingspacers projecting from the upper surface of said tongue depressingguard.
 34. A mouthpiece as claimed in claim 33 wherein said gasespassageway is provided by an insert of substantially stiffer materialthan the material of said vestibular shield, said insert extendingthrough said vestibular shield, and said tongue depressing guardincludes therein an extension of said insert forming a stiff backbonetherefor.
 35. A mouthpiece as claimed in claim 10 wherein saidmouthpiece includes extra-oral sealing means.
 36. A mouthpiece asclaimed in claim 10 wherein said extra-oral sealing means may beadjusted into one of two configurations, a first configuration when saidmouthpiece is inserted into said user's mouth being substantiallyunengaged with said user's face, and a second configuration whencorrectly positioned in said user's mouth being substantially engagedwith said user's face and under compression thereupon.
 37. A mouthpiececomprising: a vestibular shield having an inner surface and an outersurface, said vestibular shield having a predetermined height which willoverlap a user's teeth and gums when positioned in the mouth vestibuleof a user; gases passageway means extending from said outer surface ofsaid vestibular shield to said inner surface of said vestibular shieldfor allowing the passage of said gases through said mouthpiece; andextra-oral sealing means associated with said gases passageway which maybe adjusted into one of two configurations, a first condition when saidmouthpiece is inserted into a user's mouth being substantially unengagedwith a user's face, and a second condition when correctly positioned ina user's mouth being substantially engaged with a user's face and undercompression thereupon.
 38. A mouthpiece as claimed in claim 37 whereinsaid extra-oral sealing means are detachable from said gases passageway.39. A mouthpiece as claimed in claim 37 wherein said extra-oral sealingmeans are constructed of silicon rubber.
 40. A mouthpiece as claimed inclaim 37 wherein said extra-oral sealing means comprise at least onetapered flap.
 41. A mouthpiece as claimed in claim 40 wherein said flaphas a wide end and a narrow end, said narrow end being attached to saidgases passageway.
 42. A mouthpiece as claimed in claim 41 wherein saidfirst condition comprises said wide end being distal to a user relativeto said narrow end being proximal to a user.
 43. A mouthpiece as claimedin claim 41 wherein said second condition comprises said wide end beingproximal to a user relative to said narrow end being distal to a user.44. A mouthpiece as claimed in claim 37 wherein the compressive forcebetween said vestibular shield and said extra-oral sealing means on thearea surrounding a user's lips is sufficient to secure said mouthpiecein place on a user and to provide a substantial seal thereto.
 45. Amouthpiece as claimed in claim 41 wherein said wide end is adapted toconform to the facial contours of a user.
 46. A mouthpiece as claimed inclaim 40 wherein said flap includes at least one ventilation means,proximal to said narrow end.
 47. A mouthpiece as claimed in claim 46wherein said narrow end and said at least one ventilator means aresurrounded by a ridge on the side of said flap which in use faces auser.
 48. A mouthpiece as claimed in claim 46 wherein said at least oneventilator means comprises two apertures either side of said narrow end.49. A mouthpiece as claimed in claim 48 wherein said mouthpiece includesmeans which are adapted to direct a small amount of pressurised gases inthe vicinity of said apertures.
 50. A system capable of being used fororal delivery of gases pressurized above ambient to a user comprising:gases supply means, a gases passageway in fluid communication with saidgases supply means, and a mouthpiece in fluid communication with saidgases passageway including an intra-oral sealing means and an extra-oralsealing means.
 51. A system as claimed in claim 50 wherein saidextra-oral sealing means may be adjusted into one of two conditions, afirst condition when said mouthpiece is inserted into said user's mouthbeing substantially unengaged with said user's face, and a secondcondition when correctly positioned in said user's mouth beingsubstantially engaged with said user's face and under compressionthereupon.
 52. A system as claimed in claim 50 wherein said intra-oralsealing means comprise: a vestibular shield having an inner surface andan outer surface, said vestibular shield having a predetermined heightwhich will overlap a user's teeth and gums when positioned in the mouthvestibule of a user, gases passageway means extending from said outersurface of said vestibular shield to said inner surface of saidvestibular shield for allowing the passage of said gases through saidmouthpiece.
 53. A system as claimed in claim 50 wherein said extra-oralsealing means are detachable from said mouthpiece.
 54. A system asclaimed in claim 50 wherein, said extra-oral sealing means areconstructed of silicon rubber.
 55. A system as claimed in claim 52wherein said extra-oral sealing means comprise at least one taperedflap.
 56. A system as claimed in claim 55 wherein said flap has a wideend and a narrow end, said narrow end being attached to said gasespassageway.
 57. A system as claimed in claim 56 wherein said firstcondition comprises said wide end being distal to said user relative tosaid narrow end being proximal to said user.
 58. A system as claimed inclaim 56 wherein said second condition comprises said wide end beingproximal to a user relative to said narrow end being distal to saiduser.
 59. A system as claimed in claim 52 wherein the compressive forcebetween said vestibular shield and said extra-oral sealing means on thearea surrounding said user's lips is sufficient to secure saidmouthpiece in place on said user and to provide a substantial sealthereto.
 60. A system as claimed in claim 56 wherein said wide end isadapted to conform to the facial contours of said user.
 61. A system asclaimed in claim 55 wherein said flap includes at least one ventilationmeans, proximal to said narrow end.
 62. A system as claimed in claim 61wherein said narrow end and said at least one ventilator means aresurrounded by a ridge on the side of said flap which in use faces auser.
 63. A system as claimed in claim 61 wherein said at least oneventilator means comprises two apertures either side of said narrow end.64. A system as claimed in claim 63 wherein, said mouthpiece includesmeans which are adapted to direct a small amount of pressurised gases inthe vicinity of said apertures.
 65. A system as claimed in claim 51wherein said system further comprises humidification means disposed inthe flow path at said gases between said gases supply means and saidmouthpiece, adapted to humidify said gases to a desired level ofhumidity.